The present invention relates to transport vehicles such as semi-trailers and in particular to semi-trailers adapted to haul containerized or palletized loads, and more particularly relates to a method of loading and unloading such vehicles and apparatus to facilitate loading and unloading.
The difficulties in loading and unloading of heavy loads on and off trailers in the absence of suitable loading platforms or where the height of a loading platform does not match that of the trailer are well known in the art. Several versions of tiltable trailers have been suggested in the past, none of which, however, combine the advantages of critical control of heavy loads during the loading and off-loading operation with simplicity and efficiency.
The present invention resides in an improvement in a flat bed trailer tiltably attachable to a hauling unit, comprising a flat bed platform provided, on its lower surface, with at least two longitudinal carriage guiderails, a moveable wheel carriage assembly provided with rollers which engage the said carriage guiderails, the improvement comprising: (1) a winch; (2) a winch cable engaged by the said winch and capable of being selectively connected to the forward lower edge of the said container or to the forward part of the said wheel carriage assembly; (3) a linkage cable, one end of which is capable of being connected to the forward lower edge of a load, while the other end is capable of being connected to the rear part of the said wheel carriage assembly; (4) an idler sheave located at the rear of the said flat bed trailer, adapted to accept and guide said linkage cable.
Thus, the present invention provides a trailer, the rear end of which may be lowered to match the height of a loading platform or even to ground level. To achieve this end, the bed of the trailer is a tiltable platform which can be tilted rearwardly by drawing the wheel carriage of the trailer forward with respect to the trailer bed. To facilitate loading and unloading and to assure better balance of the load on the tiltable trailer when the trailer is being tilted or returned to its normal horizontal position, the loading or off-loading of the load, i.e. a container, pallet, etc. is synchronous with the tilting movement of the trailer.
The present invention further provides a method of loading containers, pallets and similar loads onto flat bed trailers having a slidably mounted wheel carriage, comprising the steps of aligning the rear end of the trailer with the front end of the load, tilting the flat bed trailer rearward by moving the slidably mounted wheel carriage in the forward direction, attaching one end of a linkage cable to the rear part of the slidably mounted wheel carriage and attaching the other end of the linkage cable to the lower forward part of the load, attaching a winch cable to the lower forward part of the load, pulling the container or pallet forward and onto the tilted trailer bed by means of the winch cable while simultaneously drawing the slidably mounted wheel carriage rearward by means of the linkage cable.
The present invention further provides a method of unloading of containers, pallets or similar loads from flat bed trailers having slidably mounted wheel carriage assemblies, comprising the steps of attaching a winch cable to the forward part of the slidably mounted wheel carriage, attaching one end of a linkage cable to the rear part of the slidably mounted wheel carriage and attaching the other end of the linkage cable to the forward lower part of the load, drawing the slidably mounted wheel carriage forward by means of the winch cable, while the load is simultaneously drawn rearward by means of the linkage cable, resulting in the trailer bed being tilted rearward and the load sliding and being drawn off the trailer bed. After a part of the load comes into contact with, and to rest, on a load bearing surface, linkage cable is disconnected the tilted flat bed trailer driven foreard and from under the remainder of the load.